U.S. patent application number 13/505457 was filed with the patent office on 2014-03-13 for led constant-current drive circuit.
The applicant listed for this patent is GAO Yuan. Invention is credited to Yuan Gao, Yubo Qiao.
Application Number | 20140070715 13/505457 |
Document ID | / |
Family ID | 47176197 |
Filed Date | 2014-03-13 |
United States Patent
Application |
20140070715 |
Kind Code |
A1 |
Gao; Yuan ; et al. |
March 13, 2014 |
LED constant-current drive circuit
Abstract
An LED constant-current drive circuit includes a BUCK circuit
consisting of a transformer T1, a diode D9, a capacitor C5 and a
field effect transistor Q1; a voltage limiting circuit consisting
of a resistor R1, a diode D8, a capacitor C1, a resistor R3, a
triode Q2, a zener diode DZ1 and a diode D10; and a current
limiting circuit consisting of a resistor R4, a triode Q3, a triode
Q4 and a resistor R2. When the transistor Q1 is turned on, a
current flows through a primary side of the transformer T1 and an
LED load, and then flows through the transistor Q1 and the resistor
R2, and then flows back to a negative electrode of a power supply.
When the transistor Q1 is turned off, the current flows through the
primary side of the transformer T1, the LED load and the diode D9,
thus forming a loop.
Inventors: |
Gao; Yuan; (Shenzhen,
CN) ; Qiao; Yubo; (Shenzhen, CN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Yuan; GAO |
Guangdong |
|
CN |
|
|
Family ID: |
47176197 |
Appl. No.: |
13/505457 |
Filed: |
February 13, 2012 |
PCT Filed: |
February 13, 2012 |
PCT NO: |
PCT/CN12/71060 |
371 Date: |
May 2, 2012 |
Current U.S.
Class: |
315/187 ;
315/291 |
Current CPC
Class: |
H05B 45/37 20200101;
H05B 45/375 20200101 |
Class at
Publication: |
315/187 ;
315/291 |
International
Class: |
H05B 33/08 20060101
H05B033/08 |
Foreign Application Data
Date |
Code |
Application Number |
May 19, 2011 |
CN |
201110129551.4 |
Claims
1-5. (canceled)
6. An LED (light emitting diode) constant-current drive circuit,
comprising: a BUCK circuit consisting of a transformer T1, a diode
D9, a capacitor C5 and a field effect transistor Q1; a voltage
limiting circuit consisting of a resistor R1, a diode D8, a
capacitor C1, a resistor R3, a triode Q2, a zener diode DZ1 and a
diode D10; and a current limiting circuit consisting of a resistor
R4, a triode Q3, a triode Q4 and a resistor R2, wherein when the
field effect transistor Q1 is turned on, a current flows through a
primary side of the transformer T1 and an LED load, and then flows
through the field effect transistor Q1 and the resistor R2, and
then flows back to a negative electrode of a power supply, and when
the field effect transistor Q1 is turned off, the current flows
through the primary side of the transformer T1, the LED load and
the diode D9, thus forming a loop.
7. The LED constant-current drive circuit, as recited in claim 6,
wherein a homonymous terminal at a primary side of the transformer
T1 is connected with a positive electrode of a power supply, the
other terminal at the primary side of the transformer T1 is
connected with an anode of an LED load, a cathode of the LED load
is connected with an anode of the diode D9 and a drain electrode of
the field effect transistor Q1, a positive electrode and a negative
electrode of the capacitor C5 are respectively connected with the
anode and the cathode of the LED load, a cathode of the diode D9 is
connected with the positive electrode of the power supply, a
homonymous terminal at a secondary side of the transformer T1 is
connected with an anode of the diode D8 and one end of the
capacitor C1, the other end at the secondary side of the
transformer T1 is connected with a source electrode of the field
effect transistor Q1, the source electrode of the field effect
transistor Q1 is connected with a negative electrode of the power
supply via the resistor R2, a gate electrode of the field effect
transistor Q1 is connected with the other end of the capacitor C1,
an emitter of the triode Q2, a cathode of the diode D10, one end of
the resistor R4 and an emitter of the triode Q3, a base of the
triode Q3 is connected with the other end of the resistor R4 and a
collector of the triode Q4, a collector of the triode Q3 is
connected with the source electrode of the field effect transistor
Q1 and a base of the triode Q4, an emitter of the triode Q4 is
connected with the negative electrode of the power supply, a
collector of the triode Q2 is connected with a cathode of the diode
D8, one end of the resistor R1 and one end of the resistor R3, the
other end of the resistor R1 is connected with the positive
electrode of the power supply, a base of the triode Q2 is connected
with the other end of the resistor R3, an anode of the diode D10
and a cathode of the zener diode DZ1, and an anode of the zener
diode DZ1 is connected with the negative electrode of the power
supply.
8. The LED constant-current drive circuit, as recited in claim 6,
wherein the triode Q3 is a PNP triode, and the triodes Q2 and Q4
are NPN triodes.
9. The LED constant-current drive circuit, as recited in claim 7,
wherein the triode Q3 is a PNP triode, and the triodes Q2 and Q4
are NPN triodes.
10. The LED constant-current drive circuit, as recited in claim 6,
wherein the field effect transistor Q1 is an enhanced PMOSFET
(p-type metal-oxide-semiconductor field effect transistor).
11. The LED constant-current drive circuit, as recited in claim 7,
wherein the field effect transistor Q1 is an enhanced PMOSFET
(p-type metal-oxide-semiconductor field effect transistor).
12. The LED constant-current drive circuit, as recited in claim 8,
wherein the field effect transistor Q1 is an enhanced PMOSFET
(p-type metal-oxide-semiconductor field effect transistor).
13. The LED constant-current drive circuit, as recited in claim 9,
wherein the field effect transistor Q1 is an enhanced PMOSFET
(p-type metal-oxide-semiconductor field effect transistor).
14. The LED constant-current drive circuit, as recited in claim 6,
wherein the LED load is formed by a plurality of LEDs connected
with each other in series.
15. The LED constant-current drive circuit, as recited in claim 7,
wherein the LED load is formed by a plurality of LEDs connected
with each other in series.
16. The LED constant-current drive circuit, as recited in claim 8,
wherein the LED load is formed by a plurality of LEDs connected
with each other in series.
17. The LED constant-current drive circuit, as recited in claim 9,
wherein the LED load is formed by a plurality of LEDs connected
with each other in series.
18. The LED constant-current drive circuit, as recited in claim 10,
wherein the LED load is formed by a plurality of LEDs connected
with each other in series.
19. The LED constant-current drive circuit, as recited in claim 11,
wherein the LED load is formed by a plurality of LEDs connected
with each other in series.
20. The LED constant-current drive circuit, as recited in claim 12,
wherein the LED load is formed by a plurality of LEDs connected
with each other in series.
21. The LED constant-current drive circuit, as recited in claim 13,
wherein the LED load is formed by a plurality of LEDs connected
with each other in series.
Description
BACKGROUND OF THE PRESENT INVENTION
[0001] 1. Field of Invention
[0002] The present invention relates to an LED (light emitting
diode) drive circuit, and more particularly to an LED
constant-current drive circuit.
[0003] 2. Description of Related Arts
[0004] LEDs are quickly applied to all areas for long service life,
high luminous efficiency, low power consumption and no radiation
characteristics in our daily life. However, the PN junction of the
LEDs also has the same characteristic of that of the diode
(nonlinearity) and has a negative temperature coefficient.
Therefore, while using the LEDs, it is required for the driving
power to have a high stability and a constant current
characteristic. The resistance-capacitance driving circuit is a
commonly used LED driving circuit. Under the high voltage, its
current increases sharply, its power factor is lower and its higher
harmonic is more. Currently, there are also some special LED
constant-current drive chips with high stability and good
constant-current characteristic on the market. However, these
special LED constant-current drive chips have complicated
structure, high cost and high price.
SUMMARY OF THE PRESENT INVENTION
[0005] An object of the present invention is to overcome the
shortcomings of the prior art and provide an LED (light emitting
diode) constant-current drive circuit with simple structure,
reliable performance and low price.
[0006] Accordingly, in order to accomplish the object mentioned
above, the present invention provides an LED (light emitting diode)
constant-current drive circuit, comprising:
[0007] a BUCK circuit consisting of a transformer T1, a diode D9, a
capacitor C5 and a field effect transistor Q1;
[0008] a voltage limiting circuit consisting of a resistor R1, a
diode D8, a capacitor C1, a resistor R3, a triode Q2, a zener diode
DZ1 and a diode D10; and a current limiting circuit consisting of a
resistor R4, a triode Q3, a triode Q4 and a resistor R2,
[0009] wherein when the field effect transistor Q1 is turned on, a
current flows through a primary side of the transformer T1 and an
LED load, and then flows through the field effect transistor Q1 and
the resistor R2, and then flows back to a negative electrode of a
power supply, and when the field effect transistor Q1 is turned
off, the current flows through the primary side of the transformer
T1, the LED load and the diode D9, thus forming a loop.
[0010] Also, the present invention provides an LED (light emitting
diode) constant-current drive circuit comprising a resistor R1, a
resistor R2, a resistor R3, a resistor R4, a capacitor C1, a
capacitor C5, a transformer T1, a diode D8, a diode D9, a diode
D10, a zener diode DZ1, a field effect transistor Q1, a triode Q2,
a triode Q3 and a triode Q4, wherein a homonymous terminal at a
primary side of the transformer T1 is connected with a positive
electrode of a power supply, the other terminal at the primary side
of the transformer T1 is connected with an anode of an LED load, a
cathode of the LED load is connected with an anode of the diode D9
and a drain electrode of the field effect transistor Q1, a positive
electrode and a negative electrode of the capacitor C5 are
respectively connected with the anode and the cathode of the LED
load, a cathode of the diode D9 is connected with the positive
electrode of the power supply, a homonymous terminal at a secondary
side of the transformer T1 is connected with an anode of the diode
D8 and one end of the capacitor C1, the other end at the secondary
side of the transformer T1 is connected with a source electrode of
the field effect transistor Q1, the source electrode of the field
effect transistor Q1 is connected with a negative electrode of the
power supply via the resistor R2, a gate electrode of the field
effect transistor Q1 is connected with the other end of the
capacitor C1, an emitter of the triode Q2, a cathode of the diode
D10, one end of the resistor R4 and an emitter of the triode Q3, a
base of the triode Q3 is connected with the other end of the
resistor R4 and a collector of the triode Q4, a collector of the
triode Q3 is connected with the source electrode of the field
effect transistor Q1 and a base of the triode Q4, an emitter of the
triode Q4 is connected with the negative electrode of the power
supply, a collector of the triode Q2 is connected with a cathode of
the diode D8, one end of the resistor R1 and one end of the
resistor R3, the other end of the resistor R1 is connected with the
positive electrode of the power supply, a base of the triode Q2 is
connected with the other end of the resistor R3, an anode of the
diode D10 and a cathode of the zener diode DZ1, and an anode of the
zener diode DZ1 is connected with the negative electrode of the
power supply.
[0011] Preferably, the triode Q3 is a PNP triode, and the triodes
Q2 and Q4 are NPN triodes.
[0012] Preferably, the field effect transistor Q1 is an enhanced
PMOSFET (p-type metal-oxide-semiconductor field effect
transistor).
[0013] Preferably, the LED load is formed by a plurality of LEDs
connected with each other in series.
[0014] In the LED constant-current drive circuit of the present
invention, the homonymous terminal at the primary side of the
transformer is connected with the positive electrode of the power
supply, the other terminal at the primary side of the transformer
is connected with the anode of the LED load, the cathode of the LED
load is connected with the anode of the diode D9 and the drain
electrode of the field effect transistor Q1, the positive electrode
and the negative electrode of the capacitor C5 are respectively
connected with the anode and the cathode of the LED load, the
cathode of the diode D9 is connected with the positive electrode of
the power supply, the homonymous terminal at the secondary side of
the transformer T1 is connected with the anode of the diode D8 and
one end of the capacitor C1, the other end at the secondary side of
the transformer T1 is connected with the source electrode of the
field effect transistor Q1, the source electrode of the field
effect transistor Q1 is connected with the negative electrode of
the power supply via the resistor R2, the gate electrode of the
field effect transistor Q1 is connected with the other end of the
capacitor C1, the emitter of the triode Q2, the cathode of the
diode D10, one end of the resistor R4 and the emitter of the triode
Q3, the base of the triode Q3 is connected with the other end of
the resistor R4 and the collector of the triode Q4, the collector
of the triode Q3 is connected with the source electrode of the
field effect transistor Q1 and the base of the triode Q4, the
emitter of the triode Q4 is connected with the negative electrode
of the power supply, the collector of the triode Q2 is connected
with the cathode of the diode D8, one end of the resistor R1 and
one end of the resistor R3, the other end of the resistor R1 is
connected with the positive electrode of the power supply, the base
of the triode Q2 is connected with the other end of the resistor
R3, the anode of the diode D10 and the cathode of the zener diode
DZ1, and the anode of the zener diode DZ1 is connected with the
negative electrode of the power supply. It can be seen that the
current flowing through the LED load is limited by controlling the
maximum current value of the inductor current of the transformer in
the LED constant-current drive circuit of the present invention.
The inductor current of the transformer can not be changed
suddenly, so the constant current is finally achieved by the linear
variation of the inductor current of the transformer, thus forming
the LED constant-current drive circuit with simple structure,
reliable performance and low price, which is adapted for the civil
LED lighting field.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] The drawing is a circuit schematic diagram of an LED (light
emitting diode) constant-current drive circuit according to a
preferred embodiment of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0016] The present invention is further detailedly explained with
the accompanying drawings.
[0017] Referring to the drawing, an LED (light emitting diode)
constant-current drive circuit according to a preferred embodiment
of the present invention is illustrated, which comprises a resistor
R1, a resistor R2, a resistor R3, a resistor R4, a capacitor C1, a
capacitor C5, a transformer T1, a diode D8, a diode D9, a diode
D10, a zener diode DZ1, an enhanced PMOSFET (p-type
metal-oxide-semiconductor field effect transistor) Q1, an NPN
triode Q2, a PNP triode Q3, and an NPN triode Q4. A homonymous
terminal at a primary side of the transformer T1 is connected with
a positive electrode of a power supply, the other terminal at the
primary side of the transformer T1 is connected with an anode of an
LED load (which is formed by a plurality of LEDs connected with
each other in series, and can also be formed by a single LED), a
cathode of the LED load is connected with an anode of the diode D9
and a drain electrode of the field effect transistor Q1, a positive
electrode and a negative electrode of the capacitor C5 are
respectively connected with the anode and the cathode of the LED
load, a cathode of the diode D9 is connected with the positive
electrode of the power supply, a homonymous terminal at a secondary
side of the transformer T1 is connected with an anode of the diode
D8 and one end of the capacitor C1, the other end at the secondary
side of the transformer Ti is connected with a source electrode of
the field effect transistor Q1, the source electrode of the field
effect transistor Q1 is connected with a negative electrode of the
power supply via the resistor R2, a gate electrode of the field
effect transistor Q1 is connected with the other end of the
capacitor C1, an emitter of the triode Q2, a cathode of the diode
D10, one end of the resistor R4 and an emitter of the triode Q3, a
base of the triode Q3 is connected with the other end of the
resistor R4 and a collector of the triode Q4, a collector of the
triode Q3 is connected with the source electrode of the field
effect transistor Q1 and a base of the triode Q4, an emitter of the
triode Q4 is connected with the negative electrode of the power
supply, a collector of the triode Q2 is connected with a cathode of
the diode D8, one end of the resistor R1 and one end of the
resistor R3, the other end of the resistor R1 is connected with the
positive electrode of the power supply, a base of the triode Q2 is
connected with the other end of the resistor R3, an anode of the
diode D10 and a cathode of the zener diode DZ1, and an anode of the
zener diode DZ1 is connected with the negative electrode of the
power supply.
[0018] In the LED constant-current drive circuit mentioned above,
the transformer T1, the diode D9, the capacitor C5 and the field
effect transistor Q1 form a buck circuit, the resistor R1, the
diode D8, the capacitor C1, the resistor R3, the triode Q2, the
zener diode DZ1 and the diode D10 form a voltage limiting circuit,
and the resistor R4, the triode Q3, the triode Q4 and the resistor
R2 form a current limiting circuit. When the field effect
transistor Q1 is turned on, the current flows through the primary
side of the transformer T1 and the LED load, and then flows through
the field effect transistor Q1 and the resistor R2, and then flows
back to the negative electrode of the power supply. When the field
effect transistor Q1 is turned off, the current flows through the
primary side of the transformer T1, the LED load and the diode D9,
thus forming a loop. Therefore, the LED constant-current drive
circuit of the present invention always works at the critical
continuous current mode, and limits the current passing through the
LED load by controlling the maximum current value of the inductor
current of the transformer. The inductor current of the transformer
can not be changed suddenly, so the constant current is finally
achieved by the linear variation of the inductor current of the
transformer.
[0019] One skilled in the art will understand that the embodiment
of the present invention as shown in the drawings and described
above is exemplary only and not intended to be limited. It will
thus be seen that the objects of the present invention have been
fully and effectively accomplished. Its embodiments have been shown
and described for the purposes of illustrating the functional and
structural principles of the present invention and is subject to
change without departure from such principles. Therefore, this
invention includes all modifications encompassed within the spirit
and scope of the following claims.
* * * * *